U.S. patent application number 14/241221 was filed with the patent office on 2014-08-14 for peak cut system.
This patent application is currently assigned to TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION. The applicant listed for this patent is Masato Hanada. Invention is credited to Masato Hanada.
Application Number | 20140225445 14/241221 |
Document ID | / |
Family ID | 47882750 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140225445 |
Kind Code |
A1 |
Hanada; Masato |
August 14, 2014 |
PEAK CUT SYSTEM
Abstract
A peak cut system which can reduce the running cost of a
power-generating device even when a peak cut process is carried
out. In a peak cut system, a control unit executes such a control
procedure that a peak cut process is first carried out only by the
discharge from a power storage device and the power generation by a
power-generating device is carried out only when a predetermined
amount of peak cut cannot be achieved only by the discharge from
the power storage device.
Inventors: |
Hanada; Masato; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hanada; Masato |
Tokyo |
|
JP |
|
|
Assignee: |
TOSHIBA MITSUBISHI-ELECTRIC
INDUSTRIAL SYSTEMS CORPORATION
Tokyo
JP
|
Family ID: |
47882750 |
Appl. No.: |
14/241221 |
Filed: |
September 13, 2011 |
PCT Filed: |
September 13, 2011 |
PCT NO: |
PCT/JP11/70782 |
371 Date: |
February 26, 2014 |
Current U.S.
Class: |
307/81 |
Current CPC
Class: |
H02J 3/32 20130101; H02J
3/38 20130101; H02J 4/00 20130101 |
Class at
Publication: |
307/81 |
International
Class: |
H02J 4/00 20060101
H02J004/00 |
Claims
1. A peak cut system comprising: a load; a power system which
carries out power supply to said load; a power-generating device
which generates power and supplies the generated power to said
load; a power storage device which carries out charge and discharge
with respect to said load; and a control unit which controls the
power supply to said load, wherein said control unit executes a
first peak cut process which carries out peak cut with respect to
power received from said power system by executing said discharge
from said power storage device, and executes a second peak cut
process which carries out said peak cut by carrying out said power
generation by said power-generating device only when a
predetermined amount of peak cut cannot be achieved only by said
discharge from said power storage device.
2. The peak cut system according to claim 1, wherein said control
unit predicts power demand and executes said first peak cut process
when the prediction value of the power demand reaches a
previously-set first target value.
3. The peak cut system according to claim 2, wherein said control
unit predicts said power demand for a predetermined demand time-out
period and stops said discharge from said power storage device at
the timing of the start of said demand time-out period.
4. The peak cut system according to claim 2, wherein said control
unit predicts said power demand and stops said discharge from said
power storage device when the prediction value of the power demand
is lowered to a previously-set second target value.
5. The peak cut system according to claim 4, wherein said control
unit carries out said charge to said power storage device after the
stop of said discharge from said power storage device.
6. The peak cut system according to claim 1, wherein said control
unit combines said power generation by said power-generating device
and said discharge from said power storage device to execute said
second peak cut process.
7. The peak cut system according to claim 1, wherein said control
unit executes said second peak cut process only by said power
generation by said power-generating device and executes said charge
to said power storage device.
8. The peak cut system according to claim 7, wherein when said
charge to said power storage device reaches a predetermined
capacity and said control unit determines that said peak cut can be
achieved only by said discharge from said power storage device,
said control unit stops said power generation by said
power-generating device to restart said first peak cut process.
9. The peak cut system according to claim 3, wherein said control
unit predicts said power demand and stops said discharge from said
power storage device when the prediction value of the power demand
is lowered to a previously-set second target value.
10. The peak cut system according to claim 9, wherein said control
unit carries out said charge to said power storage device after the
stop of said discharge from said power storage device.
Description
TECHNICAL FIELD
[0001] The present invention relates to a peak cut system in
cooperation with a power system, which carries out peak cut with
respect to power received from the power system.
BACKGROUND ART
[0002] To carry out peak cut with respect to power received from a
power system, a self-generating system in cooperation with the
power system has been introduced (for instance, Patent Documents 1
and 2).
[0003] In a technique according to Patent Document 1, a convertor
carries out conversion to charge power generated by a
power-generating device and/or power supplied from a power system
to a secondary battery or to supply power generated by the
power-generating device and power which is discharged from the
secondary battery, to a load. A controller controls the operation
of the secondary battery so that the total of the power generated
by the power-generating device and the power which is discharged
from the secondary battery is not below power consumption of the
load which exceeds a peak cut position determined by
computation.
[0004] In addition, in a technique according to Patent Document 2,
when power consumed by a load is increased, after the discharge of
power which is previously charged to efficiently operate a
power-generating device, a first self-generating device is started
so that excessive power is charged to a power storage device while
the power is outputted to the load. Then, before the start of a
second self-generating device, the power which is charged by the
first self-generating device is discharged. Further, after the
start of the second self-generating device, excessive power is
charged to the power storage device while the power is outputted to
the load. That is, in the technique according to Patent Document 2,
the procedure of the charge by a self-generating device, the
discharge from a power storage device, the charge by another
self-generating device, and the discharge from the power storage
device is repeated.
PRIOR ART DOCUMENT
Patent Document
[0005] Patent Document 1: Japanese Patent Application Laid-Open No.
2004-64810
[0006] Patent Document 2: Japanese Patent Application Laid-Open No.
2011-83044
SUMMARY OF INVENTION
Problems to be Solved by the Invention
[0007] In the techniques according to Patent Documents 1 and 2, as
shown in FIG. 2 or the like in the documents, for the peak cut,
both the power-generating device and the power storage device are
used to always drive the power-generating device. That is, in the
techniques, the driving of the power-generating device is the
essential configuration requirement for the problems to be
solved.
[0008] However, recently, the cost of fuels necessary for driving
the power-generating device has been very high. Therefore, the
problem that a high running cost is necessary for driving the
power-generating device has been serious.
[0009] Accordingly, an object of the present invention is to
provide a peak cut system which can reduce the running cost of a
power-generating device even when a peak cut process is carried
out.
Means for Solving the Problems
[0010] To achieve the above object, a peak cut system according to
the present invention includes a load, a power system which carries
out power supply to the load, a power-generating device which
generates power and supplies the generated power to the load, a
power storage device which carries out charge and discharge with
respect to the load, and a control unit which controls the power
supply to the load, wherein the control unit executes a first peak
cut process which carries out peak cut with respect to power
received from the power system by executing the discharge from the
power storage device, and executes a second peak cut process which
carries out the peak cut by carrying out the power generation by
the power-generating device only when a predetermined amount of the
peak cut cannot be achieved only by the discharge from the power
storage device.
Effects of the Invention
[0011] The peak cut system according to the present invention
includes a load, a power system which carries out power supply to
the load, a power-generating device which generates power and
supplies the generated power to the load, a power storage device
which carries out charge and discharge with respect to the load,
and a control unit which controls the power supply to the load,
wherein the control unit executes a first peak cut process which
carries out peak cut with respect to power received from the power
system by executing the discharge from the power storage device,
and executes a second peak cut process which carries out the peak
cut by carrying out the power generation by the power-generating
device only when a predetermined amount of peak cut cannot be
achieved only by the discharge from the power storage device.
[0012] Accordingly, in the present invention, for the peak cut
process, the power generation by the power-generating device can be
minimized always without the power generation by the
power-generating device. Therefore, the peak cut system according
to the present invention can prevent the power generation by the
power-generating device even when the peak cut process is carried
out in the case of increasing the running cost of the
power-generating device due to the higher fuel cost. That is, the
peak cut system can reduce the running cost of the power-generating
device.
[0013] The object, features, aspects, and advantages of the present
invention will be more apparent with reference to the following
detailed description and the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a block diagram showing the schematic
configuration of a peak cut system 100 according to an
embodiment.
[0015] FIG. 2 is a flowchart describing the operation of the peak
cut system 100 according to the embodiment.
[0016] FIG. 3 is a flowchart describing the operation of the peak
cut system 100 according to the embodiment.
[0017] FIG. 4 is a flowchart describing the operation of the peak
cut system 100 according to the embodiment.
[0018] FIG. 5 is a flowchart describing the operation of the peak
cut system 100 according to the embodiment.
[0019] FIG. 6 is a flowchart describing the operation of the peak
cut system 100 according to the embodiment.
[0020] FIG. 7 is a concept chart describing the operation of the
peak cut system 100 according to the embodiment.
[0021] FIG. 8 is a concept chart describing the operation of the
peak cut system 100 according to the embodiment.
[0022] FIG. 9 is a concept chart describing the operation of the
peak cut system 100 according to the embodiment.
[0023] FIG. 10 is a concept chart describing the operation of the
peak cut system 100 according to the embodiment.
DESCRIPTION OF EMBODIMENT
[0024] Hereinafter, the present invention will be specifically
described with reference to the drawings showing its
embodiment.
Embodiment
[0025] FIG. 1 is a schematic diagram showing the configuration of a
peak cut system 100 according to the embodiment of the present
invention.
[0026] As shown in FIG. 1, the peak cut system 100 according to
this embodiment includes a load 1, a power storage device 2, a
control unit 3, a PCS (Power Conditioning Subsystem) 4, a
power-generating device 5, a power receiving unit 6, and a power
system 7.
[0027] The load 1 is installed in an electrical system on the
demander side. The load 1 is an electric device including
electrical equipment and the like operated with power supply, and
is installed in a plant and a building and the like. In FIG. 1,
only one load 1 is shown, but a plurality of loads 1 may be
installed. In addition to power supply from the power system 7, the
load 1 can receive the supply of power which is discharged from the
power storage device 2, and can receive the supply of power
generated by the power-generating device 5.
[0028] The power system 7 is a power generation, transformation,
and transmission system and the like for supplying power to the
load 1 of the demander. That is, power supplied from the power
system 7 means power supplied from a power company to the load 1 of
the demander. The power supplied from the power system 7 can
contribute to the charge to the power storage device 2.
[0029] The power receiving unit 6 receives power supplied from the
power system 7, and outputs the received power to the load 1 and
the power storage device 2 and the like. The power receiving unit 6
is the boundary between the power system 7 side and the electrical
system on the demander side of the load 1.
[0030] The power storage device 2 is installed in the electrical
system on the demander side. The power storage device 2 includes at
least one or more batteries. Here, each battery is a secondary
battery in which charge and discharge response is quick (that is,
charge and discharge ability "C (amperetime) is high (=several C or
more)"). As the battery, for instance, a lithium ion battery can be
adopted.
[0031] The power storage device 2 can charge power received by the
power receiving unit 6 and power generated and outputted by the
power-generating device 5. In addition, the power storage device 2
carries out discharge, and can supply discharged power to the load
1.
[0032] The PCS 4 is installed in the electrical system on the
demander side. The PCS 4 includes an inverter and the like, and can
convert power which is discharged from the power storage device 2
to power usable in the load 1. The PCS 4 converts alternating
current power from the electrical system on the demander side to
direct current power for the charge to the power storage device 2,
and converts direct current power discharged from the power storage
device 2 to alternating current power usable in the load 1.
[0033] The power-generating device 5 is installed in the electrical
system on the demander side. The power-generating device 5 can
supply generated power to the load 1. The power generated by the
power-generating device 5 can contribute to the charge to the power
storage device 2. The number of power-generating devices 5 is not
limited to one, and may be plural. As the power-generating device
5, for instance, a device which generates power by using a fuel,
such as oil, is adopted.
[0034] The control unit 3 is installed on the demander side. In
addition, as shown in FIG. 1, the control unit 3 is mutually
connected to the load 1, the power storage device 2, the PCS 4, the
power-generating device 5, and the power receiving unit 6 to
bidirectionally communicate therewith via a network communication
network.
[0035] The control unit 3 uses the network structure to monitor and
manage the power used state in the load 1, the state of power
received from the power system 7 in the power receiving unit 6, the
power generated and supplied state in the power-generating device
5, the charged and discharged state in the power storage device 2,
and the remaining capacity of the power storage device 2. In
addition, the control unit 3 uses the network structure to control
power supply to the load 1. Specifically, the control unit 3 uses
the network structure to control the charge and discharge to and
from the power storage device 2 and the power generation and the
stop of the power generation by the power-generating device 5.
[0036] As described above, the control unit 3 monitors and manages
the power used state in the load 1, and calculates the prediction
value of power demand in the load 1 through the monitoring and
management. The control unit 3 can directly monitor the power used
state in the load 1. Alternatively, for instance, the control unit
3 can indirectly monitor the power used state in the load 1 from
the monitoring of power received by the power receiving unit 6, the
monitoring of power which is charged and discharged to and from the
power storage device 2, and the monitoring of power generated by
the power-generating device 5 and the like.
[0037] Power demand is a well-known term, and is an average power
used amount (kW) of the load 1 at a predetermined demand time-out.
As the predetermined demand time-out, 30 minutes is typically
adopted. That is, typically, power demand is continuously
calculated for each 30-minute period.
[0038] For instance, when the predetermined demand time-out is 30
minutes, a total power used amount (kWh) of the load 1 for 30
minutes is calculated. Then, a value obtained by dividing the
calculated total power used amount by 30 minutes (=the total power
used amount for 30 minutes/30 minutes) is the power demand for 30
minutes.
[0039] As described above, the control unit 3 predicts power
demand. The technique for predicting power demand is well-known,
and is disclosed in e.g., Japanese Patent Application Laid-Open No.
8-63132 as Patent Document.
[0040] Typically, the power used amount of the load 1 at the
completion of demand time-out is predicted from the current power
used amount of the load 1 and a gradient relative to time of the
current power used amount, so that the predicted power used amount
is then divided by demand time-out. Thus, power demand can be
predicted.
[0041] The control unit 3 according to this embodiment uses a
predicted power demand, a set target value, and the electrical
capacity of the power storage device 2 and the like to execute the
following control.
[0042] That is, when the necessity for peak cut arises from the
predicted power demand, the control unit 3 carries out control to
start the discharge from the power storage device 2 while
continuing power supply from the power system 7. A first peak cut
process which carries out the peak cut with respect to power
received from the power system 7 by executing the discharge from
the power storage device 2 is executed. Further, the control unit 3
carries out control to start the power generation by the
power-generating device 5 only when a predetermined amount of peak
cut cannot be achieved by the discharge from the power storage
device 2.
[0043] That is, in the present invention, when the predetermined
amount of peak cut can be achieved only by the discharge from the
power storage device 2, the control unit 3 prevents the
power-generating device 5 from executing the power generation (this
means that in the present invention, the peak cut process can be
carried out only by the discharge from the power storage device 2,
and in the present invention, the power generation by the
power-generating device 5 is not carried out for the peak cut
process at all times).
[0044] As described above, the peak cut only by the discharge from
the power storage device 2 (that is, the peak cut without the power
generation by the power-generating device 5) is referred to as the
first peak cut process. On the contrary, the peak cut with the
power generation by the power-generating device 5 is referred to as
a second peak cut process.
[0045] Hereinafter, the operation of the peak cut system 100
according to this embodiment will be specifically described with
reference to FIGS. 2 to 6.
[0046] Here, a first target value and a second target value are
previously set to the control unit 3. The first target value or the
second target value is selected according to whether or not a
predetermined amount of peak cut by the discharge from the power
storage device 2 is necessary.
[0047] When the prediction value of power demand is the first
target value or more, the discharge from the power storage device 2
is started. On the other hand, when the prediction value of the
power demand is the second target value or less, the discharge from
the power storage device 2 is stopped. Here, in consideration of
historical, as the second target value, a value which is slightly
smaller than the first target value is adopted.
[0048] When the prediction value of the power demand is the second
target value or less, the charge to the power storage device 2 may
be started with the stop of the discharge from the power storage
device 2. In the case, in consideration of excessive power supplied
from the power system 7 with respect to the driving of the load 1,
the second target value which is smaller than the first target
value is selected.
[0049] First, it is assumed that the power storage device 2 does
not carry out the discharge, the power-generating device 5 does not
carry out the power generation, and the load 1 receives only power
supply from the power system 7. When the power storage device 2 is
not fully charged, the charge is executed by using power received
from the power system 7.
[0050] As shown in step S1 in FIG. 2, the control unit 3 calculates
the prediction value of the power demand at all times (or
regularly). Further, the control unit 3 determines whether or not
the power demand predicted in step S1 is the first target value or
more (step S2).
[0051] The used power amount of the load 1 is increased, so that
the prediction value of the power demand reaches the first target
value (in step S2, "Y"). In the case, there is the necessity for
the peak cut process, so that the control of the control unit 3
starts the discharge from the power storage device 2 (step S3).
That is, the above-described first peak cut process is started.
Here, the power generation by the power-generating device 5 is left
stopped.
[0052] On the other hand, the prediction value of the power demand
is less than the first target value (in step S2, "N"). In the case,
the peak cut process is unnecessary, so that the control unit 3
does not execute the discharge from the power storage device 2 and
the power generation by the power-generating device 5, and then the
process in step S1 is carried out again. That is, the operation
after step S1 is repeatedly executed.
[0053] Here, the control unit 3 considers the power used state in
the load 1 (that is, the prediction value of the power demand), and
determines that the power supplied from the power system 7 affords
the driving of the load 1. In the case, when the capacity of the
power storage device 2 is not fully charged, the control of the
control unit 3 carries out the charge to the power storage device 2
during the repeated operation in steps S1 and S2 in FIG. 2.
[0054] When the first peak cut process is started in step S3, the
control unit 3 executes each operation shown in FIGS. 3, 4, and
5.
[0055] First, the flow in FIG. 3 will be described.
[0056] As described in step S1 in FIG. 2, the control unit 3
continues the calculation of the prediction value of the power
demand. In step S3 in FIG. 2, the discharge from the power storage
device 2 is started. As shown in step S10 in FIG. 3, the discharge
from the power storage device 2 is continued. In the state, the
control unit 3 carries out determination in step S11. That is, the
control unit 3 determines whether or not the predicted power demand
is the second target value or less (step S11).
[0057] The used power amount of the load 1 is reduced, so that the
prediction value of the power demand is lowered to the second
target value (in step S11, "Y"). The case is a case where the
necessity for the peak cut process is eliminated, so that the
control of the control unit 3 stops the discharge from the power
storage device 2 (step S12). That is, the above-described first
peak cut process is stopped. Thereafter, the control unit 3
executes the series of operations shown in FIG. 2.
[0058] Here, the first peak cut process (that is, the discharge
from the power storage device 2) reduces the capacity of the power
storage device 2. Accordingly, after step S12, the control unit 3
considers the power used state in the load 1 (that is, the
prediction value of the power demand), and determines that the
power supplied from the power system 7 affords the driving of the
load 1. In the case, the control unit 3 controls the power storage
device 2 to start the charge to the power storage device 2.
[0059] Alternatively, in step S12, (that is, the prediction value
of the power demand is lowered to the second target value), the
control of the control unit 3 may start the charge to the power
storage device 2 with the stop of the discharge from the power
storage device 2.
[0060] On the other hand, the prediction value of the power demand
is larger than the second target value (in step S11, "N"). The case
is a case where the necessity for the peak cut process is
continued. The discharge from the power storage device 2 is
continued (step S10), and then the operation after step S10 is
repeatedly executed.
[0061] In addition, in the flow in FIG. 4, the discharge from the
power storage device 2 is stopped. The flow in FIG. 4 will be
described.
[0062] As described above, the power demand is continuously
calculated for the predetermined demand time-out period. That is,
in the case where the predetermined demand time-out is 30 minutes,
when the calculation of the power demand for next 30 minutes in the
range of 0 to 30 minutes is completed, the calculation of new power
demand for 30 minutes in the range of 30 to 60 minutes is started.
That is, the value of the power demand is reset to zero at the
timing of the start of the next predetermined demand time-out
period.
[0063] As described in step S1 in FIG. 2, the control unit 3
continues the calculation of the prediction value of the power
demand. In step S3 in FIG. 2, the discharge from the power storage
device 2 is started. As shown in step S20 in FIG. 4, the discharge
from the power storage device 2 is continued. In the state, the
control unit 3 carries out determination in step S21. That is, the
control unit 3 determines whether or not a new demand time-out
period is started for the predetermined demand time-out period
(step S21).
[0064] It is assumed that the control unit 3 predicts the power
demand for the predetermined demand time-out period, a certain
predetermined demand time-out period is ended, and then the next
demand time-out period is started (in step S21, "Y"). Then, at the
timing of the start of the next demand time-out period, the control
of the control unit 3 stops the discharge from the power storage
device 2 (step S22). That is, the above-described first peak cut
process is stopped once. Thereafter, the control unit 3 executes
the series of operations shown in FIG. 2.
[0065] On the other hand, it is assumed that the control unit 3
predicts the power demand for the predetermined demand time-out
period, and a certain predetermined demand time-out period has not
been ended yet. For instance, it is assumed that the predetermined
demand time-out period is 30 minutes, and then, in the demand
time-out period for t to t+30 minutes, determination time T in step
S21 is t<T<t+30 minutes (in step S21, "N"). In the case, the
discharge from the power storage device 2 is continued (step S20),
so that the operation after step S20 in FIG. 4 is repeatedly
executed.
[0066] The flow in FIG. 4 can be considered to be the same as the
flow in FIG. 3. That is, as described above, at the timing of the
start of the next predetermined demand time-out period, the value
of the power demand is reset to zero (for the next predetermined
demand time-out period, the prediction value of the power demand is
calculated from zero). In the case, the prediction value of the
power demand is the second target value or less in step S1 1 in
FIG. 3. Therefore, without additionally providing the flow in FIG.
4, only the flow in FIG. 3 may be provided. However, in this
embodiment, for the detailed description of the invention, in
addition to the flow in FIG. 3, the flow in FIG. 4 is additionally
provided.
[0067] In addition, the change in the demand prediction value is
large immediately after the start of the demand time-out in FIG. 4.
Therefore, any constant period immediately after the start of the
demand time-out can also be a charge and discharge inhibition time
zone.
[0068] As described above, after the start of the discharge from
the power storage device 2 in the flow in FIG. 2, the control unit
3 executes the operation of the flow shown in FIG. 5 while
executing the flows in FIGS. 3 and 4. Next, the flow in FIG. 5 will
be described.
[0069] As described in step S1 in FIG. 2, the control unit 3
continues the calculation of the prediction value of the power
demand. In step S3 in FIG. 2, the discharge from the power storage
device 2 is started. As shown in step S30 in FIG. 5, the discharge
from the power storage device 2 is continued. In the state, the
control unit 3 carries out determination in step S31. That is, from
the prediction value of the power demand and the remaining capacity
of the power storage device 2 obtained by monitoring the power
storage device 2, the control unit 3 determines whether or not a
predetermined amount of peak cut cannot be achieved only by the
discharge from the power storage device 2 (step S31).
[0070] Due to the increasing of the prediction of the power demand
and/or the decreasing of the remaining capacity of the power
storage device 2, the control unit 3 determines that the
predetermined amount of peak cut cannot be achieved only by the
discharge from the power storage device 2 (in step S31, "Y"). In
the case, the control unit 3 controls the power-generating device
5, so that the power-generating device 5 starts the power
generation (step S32). That is, the above-described second peak cut
process is executed.
[0071] Here, after step S32, from the prediction value of the power
demand and the power generation force from the power-generating
device 5, the control unit 3 determines that the predetermined
amount of peak cut with respect to the power system 7 can be
achieved to some extent only by the generated power from the
power-generating device 5. In the case, the control of the control
unit 3 executes the second peak cut process only by the
power-generating device 5. That is, the control unit 3 controls the
power storage device 2, stops the discharge from the power storage
device 2, and starts the charge to the power storage device 2.
[0072] On the contrary, after step S32, from the prediction value
of the power demand and the power generation force from the
power-generating device 5, the control unit 3 determines that the
predetermined amount of peak cut with respect to the power system 7
is difficult only by the generated power from the power-generating
device 5. In the case, the control of the control unit 3 executes
the second peak cut process in which the discharge from the power
storage device 2 and the power generation by the power-generating
device 5 are combined.
[0073] After step S32, the control unit 3 executes the control in
FIGS. 2, 3, 4, and 6. Here, in step S22 in FIG. 4, the control unit
3 continues the power generation started in step S32 even when the
discharge from the power storage device 2 is stopped.
[0074] On the other hand, unlike the determination of "Y" in step
S31, the control unit 3 determines that the predetermined amount of
peak cut can be achieved only by the discharge from the power
storage device 2 (in step S31, "N"). In the case, the control unit
3 does not start the power generation by the power-generating
device 5, continues the first peak cut process only by the
discharge from the power storage device 2 (step S30), and
repeatedly executes the operation after step S30.
[0075] After the operation in step S32 in FIG. 5, the control unit
3 also executes the flow operation in FIG. 6. Next, the flow in
FIG. 6 will be described.
[0076] In step S32 in FIG. 5, the power generation by the
power-generating device 5 is started. As shown in step S40 in FIG.
6, the power generation by the power-generating device 5 is
continued. In the state, the control unit 3 monitors the charged
state in the power storage device 2. Then, the control unit 3
determines whether or not the capacity of the power storage device
2 reaches a predetermined capacity which is previously set in the
control unit 3 (for instance, a fully charged state) (step
S41).
[0077] When the capacity of the power storage device 2 is less than
the predetermined capacity (in step S41, "N"), the second peak cut
process with the power generation by the power-generating device 5
is continued to repeatedly execute the operation after step
S40.
[0078] On the other hand, when the capacity of the power storage
device 2 reaches the predetermined capacity (in step S41, "Y"),
from the prediction value of the power demand for a predetermined
time (e.g., 5 minutes), the control unit 3 determines whether or
not the predetermined amount of peak cut can be achieved only by
the discharge from the power storage device 2 (step S42). That is,
from the prediction value of the power demand for the predetermined
time, even if the second peak cut process with the power generation
by the power-generating device 5 is stopped, and the first peak cut
is processed only by the discharge from the power storage device 2,
the control unit 3 determines whether or not the predetermined
amount of peak cut can be achieved.
[0079] When the control unit 3 determines that the peak cut is
difficult only by the discharge from the power storage device 2 (in
step S42, "N"), the second peak cut process with the power
generation by the power-generating device 5 is continued to
repeatedly execute the operation after step S40.
[0080] On the contrary, when determining that the peak cut can be
achieved only by the discharge from the power storage device 2 (in
step S42, "Y"), the control unit 3 controls the power-generating
device 5 to stop the power generation by the power-generating
device 5 (step S43). The control of the control unit 3 restarts the
first peak cut process only by the discharge from the power storage
device 2. Thereafter, the control unit 3 carries out the operations
shown in FIGS. 2 to 5.
[0081] Alternatively, even when the power storage device 2 is fully
charged and the peak cut can be achieved only by the power storage
device 2, the following may be carried out to avoid the repetition
of the continuous start and stop of the power-generating device 5.
That is, without stopping the power-generating device 5 until the
demand time-out in progress is completed, the power-generating
device 5 may be stopped when a new demand time-out is started.
[0082] FIGS. 7 to 10 are schematic charts which conceptually
describe the operation of the peak cut system 100 according to this
embodiment.
[0083] As shown in FIG. 7, power demand at the predetermined demand
time-out is chronologically changed. In cases A, B, and C in FIG.
7, the power demand exceeds the first target value, so that the
peak cut is necessary.
[0084] FIG. 8 shows, in case A, the chronological change in the
capacity of the power storage device 2, the chronological change in
the charge and discharge to and from the power storage device 2,
and the chronological change in the power generation by the
power-generating device 5. FIG. 9 shows, in case B, the
chronological change in the capacity of the power storage device 2,
the chronological change in the charge and discharge to and from
the power storage device 2, and the chronological change in the
power generation by the power-generating device 5. FIG. 10 shows,
in case C, the chronological change in the capacity of the power
storage device 2, the chronological change in the charge and
discharge to and from the power storage device 2, and the
chronological change in the power generation by the
power-generating device 5.
[0085] In case A, the peak cut can be achieved only by the first
peak cut process. As shown in FIG. 8, in case A, after the
prediction value of the power demand exceeds the first target value
for the first time, the power storage device 2 repeats the charge
and discharge, but the power generation by the power-generating
device 5 is not executed. At time t' in FIG. 8, after the
prediction value of the power demand is below the second target
value, the peak cut process is stopped, the charge to the power
storage device 2 is continuously executed, and the charge to the
power storage device 2 is stopped when the power storage device 2
is fully charged.
[0086] In case B, the first peak cut process and the second peak
cut process are executed. As shown in FIG. 9, in case A, after the
prediction value of the power demand exceeds the first target value
for the first time, the discharge from the power storage device 2
is continuously executed. However, the predetermined amount of peak
cut is difficult only by the discharge from the power storage
device 2, so that the second peak cut process with the
power-generating device 5 is executed. As shown in FIG. 9, the
second peak cut process is executed only by the power generation by
the power-generating device 5, and after the start of the second
peak cut process, the power storage device 2 continuously executes
the charge until it is fully charged by using excessive power from
the power-generating device 5.
[0087] As in case A, in case C, the peak cut can be achieved only
by the first peak cut process. As shown in FIG. 10, in case C,
after the prediction value of the power demand exceeds the first
target value, the discharge from the power storage device 2 is
executed, and the power generation by the power-generating device 5
is not executed. Thereafter, the prediction value of the power
demand is below the second target value, the peak cut process is
stopped, the charge to the power storage device 2 is continuously
executed, and the charge to the power storage device 2 is stopped
when the power storage device 2 is fully charged.
[0088] As described above, in the peak cut system 100 according to
this embodiment, first, the control unit 3 executes the first peak
cut process only by the discharge from the power storage device 2.
Then, only when the predetermined amount of peak cut cannot be
achieved only by the first peak cut process, the second peak cut
process with the power generation by the power-generating device 5
is executed.
[0089] That is, in the present invention, for the peak cut process,
the power generation by the power-generating device 5 can be
minimized always without the power generation by the
power-generating device 5. Therefore, even when the peak cut
process is executed at the increase of the running cost of the
power-generating device 5 due to the higher fuel cost, the peak cut
system 100 can prevent the power generation by the power-generating
device 5. That is, the peak cut system 100 can reduce the running
cost of the power-generating device 5.
[0090] In the peak cut system 100 according to this embodiment, the
control unit 3 predicts the power demand, and executes the first
peak cut process when the prediction value of the power demand
reaches the previously-set first target value.
[0091] In the peak cut system 100 according to this embodiment, the
control unit 3 predicts the power demand, and stops the discharge
from the power storage device 2 when the prediction value of the
power demand is lowered to the previously-set second target
value.
[0092] In the peak cut system 100 according to this embodiment, the
control unit 3 predicts the power demand for the predetermined
demand time-out period, and stops the discharge from the power
storage device 2 at the timing of the start of the demand time-out
period.
[0093] In this way, in the peak cut system 100, the prediction
value of the power demand is used to control the start and stop of
the first peak cut process. Therefore, the peak cut can be executed
automatically and at proper timing.
[0094] In the peak cut system 100 according to this embodiment, the
control unit 3 can also execute control to carry out the charge to
the power storage device 2 after the stop of the first peak cut
process.
[0095] Therefore, the peak cut system 100 can recover the capacity
of the power storage device 2 reduced by the first peak cut process
to the fully electrically charged state by using excessive power,
such as power supplied from the power system 7.
[0096] In the peak cut system 100 according to this embodiment, the
control unit 3 can execute the second peak cut process by combining
the power generation by the power-generating device 5 and the
discharge from the power storage device 2.
[0097] Therefore, even when the predetermined amount of peak cut is
difficult only by the power generation by the power-generating
device 5, the peak cut system 100 can realize the predetermined
amount of peak cut by using the discharge from the power storage
device 2.
[0098] In the peak cut system 100 according to this embodiment, the
control unit 3 can execute the second peak cut process only by the
power generation by the power-generating device 5. The control unit
3 can execute the charge to the power storage device 2.
[0099] Therefore, for the second peak cut process period, the peak
cut system 100 can recover the capacity of the power storage device
2 reduced by the peak cut process to the fully charged state by
using excessive power, such as power outputted from the
power-generating device 5.
[0100] In the peak cut system 100 according to this embodiment, the
control unit 3 stops the power generation by the power-generating
device 5 and restarts the first peak cut process when the charge to
the power storage device 2 reaches the predetermined capacity and
the control unit 3 determines that the peak cut can be achieved
only by the discharge from the power storage device 2.
[0101] For instance, after the start of the second peak cut
process, the prediction value of the power demand value is reduced.
In the case, when the peak cut is necessary, the second peak cut
process can be transferred to the first peak cut process.
Accordingly, after the start of the second peak cut process, the
power generation by the power-generating device 5 can be minimized.
Therefore, in the peak cut system 100, after the start of the
second peak cut process, the power generation by the
power-generating device 5 can be prevented. That is, in the peak
cut system 100, after the start of the second peak cut process, the
running cost of the power-generating device 5 can be reduced.
[0102] In the peak cut system 100 according to this embodiment, the
power storage device 2 may function as a backup power source in the
event that an abnormal condition of the power system 7, such as a
power failure, is caused.
[0103] The present invention has been described in detail, but the
above description is illustrated in all aspects, and the present
invention is not limited thereto. It will be understood that an
infinite number of non-illustrated modification examples can be
contrived without departing from the scope of the present
invention.
REFERENCE SIGNS LIST
[0104] 1 Load
[0105] 2 Power storage device
[0106] 3 Control unit
[0107] 4 PCS
[0108] 5 Power-generating device
[0109] 6 Power receiving unit
[0110] 7 Power system
[0111] 100 Peak cut system
* * * * *